JP2013139550A - Electrically conductive interconnecting porous film and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically conductive interconnecting porous film which can achieve good electrical conductivity, good gas permeability, good surface smoothness, good corrosion resistance and reduced impurity content, has high bending resistance that cannot be achieved by conventional carbon fiber sheet-like articles, has excellent handling properties, and can be used as a material for a gas diffusion layer to be used in a new polymer electrolyte fuel cell; and to provide a method for producing the same.SOLUTION: This film has a porous interconnected void 20, wherein a void part 21, formed by removing a granular material to be removed from a resin base part 10 composed of a thermoplastic resin, has a size of 10-50 μm, and a resin base part is formed by mixing first carbon particles 31 which are large-diameter carbon particles with ≥50 μm diameter and different in mutual particle diameters with second carbon particles 32 which are fine-size carbon particles with ≥10 nm.

Description

  The present invention relates to a conductive continuous porous film and a method for producing the same, and more particularly to a conductive continuous porous film that secures conductivity in a porous resin film and a method for producing the conductive continuous porous film.

  In a general polymer electrolyte fuel cell (PEFC), separators are arranged on both sides of a fuel electrode (negative electrode / anode) for supplying hydrogen and an air electrode (positive electrode / cathode) for supplying oxygen. The membrane electrode assembly is sandwiched. This membrane electrode assembly is configured by a catalyst layer, a water repellent layer on both sides of a proton conductive film, and a gas diffusion layer on the outside thereof. The gas diffusion layer diffuses the gas supplied from the separator side to the catalyst layer side to make the concentration uniform. Therefore, the gas concentration in the membrane electrode assembly is always constant, and unevenness of reaction is eliminated, so that power generation efficiency is increased.

  The first property required for such a gas diffusion layer is that it does not hinder the transport of electrons between the separator and the catalyst layer, that is, it has high conductivity. Secondly, it has good gas permeability for the convenience of supplying hydrogen and oxygen from the gas flow path of the separator to the catalyst layer and discharging water (steam) as a reaction product. Third, surface smoothness is required to prevent a short circuit due to inadvertent contact between the layers. Fourth, corrosion resistance and electrical stability are required to maintain battery performance and prolong service life. The fifth is to contain as little impurities as possible to stabilize the performance.

  As a material for the gas diffusion layer having the above characteristics, a porous metal plate or the like has been proposed, but it is inferior in corrosion resistance. In view of this, a sheet-like material in which carbon fibers and a binder are made to form a random network structure has been proposed (see Patent Documents 1, 2, 3, 4, etc.). Since the material of the gas diffusion layer disclosed in each patent document uses carbon fiber, it is excellent in conductivity and corrosion resistance and has low impurities. Moreover, since it is a network structure by papermaking, air permeability is also excellent. For this reason, the sheet-like material made of carbon fiber is the mainstream material for the gas diffusion layer used in the current polymer electrolyte fuel cell.

  However, the sheet-like material made from the carbon fiber disclosed in each of the above patent documents suppresses the amount of binder added in order to maintain high conductivity. For this reason, when it forms in 0.1 mm or less, a sheet-like thing is lacking in the tolerance to a shear force. When formed to be 0.3 mm or more, the sheet-like material is poor in flexibility and is difficult to wind. Moreover, even if it is a sheet-like material formed to 0.1 to 0.3 mm, cracking is likely to occur when it is bent. In addition, the carbon fibers are easily detached from the sheet-like material. Thus, since the sheet-like material made from carbon fiber, which is an existing material for the gas diffusion layer, is fragile, the convenience in handling during manufacture is not necessarily high.

  Therefore, there is a demand for a new conductive porous material that satisfies high conductivity, good gas permeability, surface smoothness, corrosion resistance, and low impurities, and is strong against bending and excellent in handling properties. It was.

International Publication Number WO 01/022509 International Publication Number WO 01/056103 Japanese Patent Laid-Open No. 2004-288889 JP 2006-143478 A

  The inventor has been diligently studying further use of the resin-made communicating porous material. As a result, it has been found that the resin-made continuous porous body can be applied to, for example, a gas diffusion layer used in a polymer electrolyte fuel cell.

  The present invention has been proposed in view of the above-described circumstances, and satisfies the requirements of good conductivity, good gas permeability, surface smoothness, corrosion resistance, and low impurities, and is obtained with an existing carbon fiber sheet. Provided is a porous material having new conductivity that is strong against bending and has excellent handling properties.

  That is, the invention according to claim 1 is the first carbon having a porous communicating void portion formed by removing the particulate matter to be removed from the resin base material portion, and the resin base material portions having different particle diameters. The present invention relates to a conductive continuous porous film characterized in that particles and second carbon particles are mixed.

  A second aspect of the present invention relates to the conductive continuous porous film according to the first aspect, wherein the resin base material portion is a thermoplastic resin.

  A third aspect of the present invention relates to the conductive continuous porous film according to the first aspect, wherein the size of one cavity of the porous communication void is 10 μm to 50 μm.

  The invention according to claim 4 relates to the conductive continuous porous film according to claim 3, wherein the cavity includes two or more kinds of cavities having different sizes.

  A fifth aspect of the present invention relates to the conductive continuous porous film according to the first aspect, wherein the removed granular material is water-soluble particles and is removed by water content.

  A sixth aspect of the present invention relates to the conductive continuous porous film according to the first aspect, wherein the particulate matter to be removed is starch particles and is removed by enzymatic decomposition.

  According to a seventh aspect of the present invention, the first carbon particles are large-sized carbon particles having a diameter of 5 μm or more, and the second carbon particles are fine-sized carbon particles having a diameter of 10 nm or more. Related to quality film.

  The invention according to claim 8 relates to the conductive continuous porous film according to claim 7, wherein the large-diameter carbon particles are carbon fibers.

  The invention according to claim 9 relates to the conductive continuous porous film according to claim 7, wherein the large-diameter carbon particles are spherical graphite.

  A tenth aspect of the present invention relates to the conductive continuous porous film according to the seventh aspect, wherein the minute diameter carbon particles are carbon nanotubes.

  The invention of claim 11 is a kneading step of kneading a base resin, a granular material to be removed, and first carbon particles and second carbon particles having different particle diameters to obtain a resin kneaded product, and the resin kneading A conductive continuous porous film comprising: a molding step of molding a product into a film-shaped resin molded product; and a removing step of removing the particulate matter to be removed from the film-shaped resin molded product to obtain voids. Related to manufacturing method.

  According to the conductive continuous porous film of the first aspect of the present invention, the resin base material portion has the porous communication gap formed by removing the particulate matter to be removed, and the resin base material portions are mutually connected. Since the first carbon particles and the second carbon particles having different particle diameters are mixed, satisfying good conductivity, good gas permeability, surface smoothness, corrosion resistance, and few impurities, It is possible to obtain a porous material having new conductivity that is strong in bending and excellent in handling properties, which cannot be obtained with a sheet-like material.

  According to the conductive continuous porous film of the invention of claim 2, in the invention of claim 1, since the resin base material portion is a thermoplastic resin, it has corrosion resistance and flexibility, and is further fluidized by heating and melting. Can be increased.

  According to the conductive continuous porous film of the invention of claim 3, in the invention of claim 1, since the size of one cavity of the porous communication gap is 10 μm to 50 μm, gas permeation and Diffusion and the strength of the film itself can be maintained.

  According to the conductive continuous porous film of the invention of claim 4, in the invention of claim 3, the cavity includes two or more types of cavities having different sizes. In addition to transmission performance, diffusion performance is also improved.

  According to the conductive continuous porous film of the invention of claim 5, in the invention of claim 1, since the particulate matter to be removed is water-soluble particles and is removed by water content, the removal is very simple.

  According to the conductive continuous porous film of the invention of claim 6, in the invention of claim 1, since the removed granular material is starch particles and is removed by enzymatic decomposition, the starch particles can be easily removed. Can do.

  According to the conductive continuous porous film of the invention of claim 7, in the invention of claim 1, the first carbon particles are large-diameter carbon particles having a diameter of 5 μm or more, and the second carbon particles have a diameter of 10 nm or more. Since the carbon particles are micro-sized, it is possible to obtain conductivity as well as air permeability even in a film having a resin base material part while utilizing the characteristics of two types of carbon particles having different particle sizes.

  According to the conductive continuous porous film of the invention of claim 8, in the invention of claim 7, since the large-diameter carbon particles are carbon fibers, it becomes easy to stabilize performance.

  According to the conductive continuous porous film of the ninth aspect of the invention, in the invention of the seventh aspect, since the large-diameter carbon particles are spherical graphite, it acts on a decrease in resistivity of the film itself.

  According to the conductive continuous porous film of the invention of the tenth aspect, in the invention of the seventh aspect, since the minute-diameter carbon particles are carbon nanotubes, it is easy to stabilize the performance.

  According to the method for producing a conductive continuous porous film according to the invention of claim 11, the base resin, the granular material to be removed, and the first carbon particles and the second carbon particles having different particle diameters are kneaded. A kneading step for obtaining a resin kneaded product, a molding step for molding the resin kneaded product into a film-shaped resin molded product, and a removing step for removing the particulate matter to be removed from the film-shaped resin molded product. Therefore, it is a new material that satisfies good conductivity, good gas permeability, surface smoothness, corrosion resistance, and low impurities, is strong against bending and cannot be obtained with existing carbon fiber sheets, and has excellent handling properties. A method for producing a porous material having electrical conductivity has been established.

It is a cross-sectional schematic diagram of the electroconductive continuous porous film of the present invention. It is a cross-sectional schematic diagram of another electroconductive continuous porous film. Furthermore, it is a cross-sectional schematic diagram of another electroconductive communicating porous film. It is a schematic process drawing explaining the manufacturing method of this invention. It is a schematic diagram further explaining the removal process of FIG.

  The conductive continuous porous film 1 in the present invention is formed by the resin base material portion 10 as can be understood from the schematic cross-sectional view of FIG. A porous communication gap portion 20 having a communication portion 22 is formed inside the resin base material portion 10. The porous communication void portion 20 is open to the surface of the conductive communication porous film 1. Furthermore, the first carbon particles 31 (first carbon material) and the second carbon particles 32 (second carbon material) are mixed into the resin base material 10 as two types of carbon particles having different particle diameters. The film 1 includes a resin base material portion 10 developed in a sponge shape (sponge-like shape), and the first carbon particles 31 and the second carbon particles 32 are embedded in the resin portion of the resin base material portion 10. . Therefore, the conductive continuous porous film has flexibility derived from the resin base material part, air permeability of the porous communication voids opened on both surfaces of the film, and also has conductive performance due to the carbon particles. .

  The resin base material part 10 used as the structural material of the electroconductive continuous porous film 1 is selected from thermoplastic resins. The resin material is a good example in that it has corrosion resistance and imparts flexibility to the film. Furthermore, by using a thermoplastic resin, it is melted by heating to increase fluidity. From this, it becomes possible to uniformly disperse the particulate matter 25 to be removed, the first carbon particles 31, and the second carbon particles 32, which will be described later, and further facilitate the subsequent molding.

  As the thermoplastic resin, ethylene homopolymer, propylene homopolymer, ethylene and propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc., or one or more α-olefins And a random copolymer with the above composition or a block copolymer having the above composition. Further, it is a polyolefin resin such as a mixture of these polymers described above, and a hydrocarbon resin such as petroleum resin and terpene resin. In addition, a resin excellent in corrosion resistance such as a fluororesin is also selected. The various resins listed are base resins in the method for producing a conductive continuous porous film.

  For example, when a gas diffusion layer of a polymer electrolyte fuel cell is assumed, the above-described thermoplastic polyolefin resin or fluororesin is preferably used. This is because the polyester resin contains an ester bond and the polyamide resin contains an amide bond, so that it is considered that the polyester resin is likely to deteriorate due to the influence of an acidic group such as a sulfone group of the catalyst layer.

  The porous communication void portion 20 formed inside the resin base material portion 10 has a structure in which a plurality of appropriately shaped granular cavities 21 come into contact with each other and are randomly continuous. Individual to-be-removed granular materials 25 (see FIG. 3 described later) existing in the resin base material portion 10 are removed afterwards to form a plurality of cavities 21. The communication part 22 where the resin base material part 10 does not exist is formed between the cavity parts 21 that are in contact with each other, and the porous communication cavity part 20 is formed continuously between the cavity parts 21. Around the to-be-removed granular material 25 close to the surface of the conductive continuous porous film 1, there are some portions where the resin base material portion 10 is thin or where the to-be-removed granular material 25 is exposed without being present. For this reason, in the surface of the said conductive continuous porous film 1, the opening by the cavity part 21 arises.

  The random communication between the hollow portions 21 ensures good gas permeability from the one surface side to the other surface side of the conductive communication porous film 1. At the same time, the gas diffusibility is also increased by passing through the cavity 21 of the film 1. Therefore, in consideration of the permeation and diffusion of gas and the maintenance of the strength of the film itself, the size of the hollow portion 21 of the porous communication void portion 20 is formed to a size of 10 μm to 50 μm.

  There exists melt | dissolution in water as a simple method of removing the to-be-removed granular material 25 from the resin base-material part 10 easily. It is that the resin base material part 10 containing the to-be-removed granular material 25 is water-containing. In this case, the removal granular material 25 is selected from water-soluble particles. For example, sugar crystals, glucose crystals, icing sugar, lump sugar (sugar coagulum) and the like. In the case of a salt crystal, it is a sodium chloride crystal, an alum crystal, a potassium nitrate crystal, or the like. In addition, limestone and calcium carbonate crystals that have been pulverized and classified to a predetermined particle diameter can also be mentioned. Therefore, when dissolving in water, dissolution using dilute hydrochloric acid is also added.

  The aforementioned water-soluble particles may vary in wear and shape during handling. In other words, the size of the individual cavities 21 forming the porous communication gap 20 is preferably as uniform as possible. In addition, it is desirable that each hollow portion has a rounded shape. For this requirement, starch particles are used as the particulates 25 to be removed. Starch particles are crystals of sugar chain compounds produced by plants, and the form and particle size of starch particles are about 1 to 100 μm depending on the plant species. Depending on the type of plant, the particle size is relatively uniform, which is convenient for homogenizing the removed particulate matter. For example, particles such as potato starch have an oval shape with an average particle size of about 20-40 μm, and corn starch, mung beans, tapioca starch, etc. have an average particle size of about 10-15 μm.

  In consideration of the thickness of the conductive continuous porous film, the size and amount of mixed carbon particles, the type and amount of starch particles are defined. In addition, only one type of starch particles or a mixture of a plurality of types of starch particles can be used.

  However, it is difficult to completely remove starch particles by immersing them in water or hot water. Therefore, an enzyme is added to water or hot water for easy removal from the resin base material portion 10, and the starch particles to be removed 25 are decomposed and removed by the enzyme. That is, the correspondence between the removed particulate matter and the enzyme depends on the substrate specificity between them. Therefore, α-amylase, β-amylase, pullulanase and the like are selected as the enzyme.

  As a feature of the conductive continuous porous film 1 of the present invention, two types of carbon particles (first carbon particles 31 and second carbon particles 32) having different particle diameters are dispersed and mixed in the resin base material portion 10. Yes. The first carbon particles 31 are particles having a particle size 100 to 1000 times larger than the second carbon particles 32.

  More specifically, the first carbon particles 31 are large diameter carbon particles 33 (large diameter carbon material) having a diameter of 5 μm or more and about 150 μm or less, and the second carbon particles 32 are fine diameter carbon particles having a diameter of 10 nm or more and about 150 nm or less. 34 (small-diameter carbon material). As shown in the schematic diagram of FIG. 1, large-diameter carbon particles 33 and small-diameter carbon particles 34 are randomly present in the resin base material portion 10. The reason why two kinds of carbon particles having extremely different particle diameters are used instead of carbon particles of any size is based on the results of the examples described later.

  The reason is presumed as follows. When only the minute diameter carbon particles 34 are mixed into the resin base material portion 10, the surface area of the minute diameter carbon particles 34 itself is large, so that the viscosity is likely to increase during kneading with the base resin. Therefore, it is difficult to increase the blending amount of the small-diameter carbon particles 34 for the purpose of improving the conductivity of the resin base material portion. Further, when only the large-diameter carbon particles 33 are mixed in the resin base material portion 10, it is possible to increase the blending amount per weight as compared with the small-diameter carbon particles 34. However, the space | interval of the large diameter carbon particles 33 becomes wide, and the site | part only of the resin base material part 10 with few electroconductivity also appears on the film surface. For this reason, it becomes a restriction | limiting of the electroconductivity improvement.

  Therefore, the above-mentioned restrictions were dealt with by blending both large-diameter carbon particles 33 and small-diameter carbon particles 34. Although the large-diameter carbon particles 33 of the conductive continuous porous film 1 can be close to each other and come into contact with each other depending on the blending amount, they can act as a conduction site in the resin base material portion and can improve conductivity. And since the small diameter carbon particle 34 exists also in the resin base material parts 10 other than the large diameter carbon particle 33, the electroconductive fall of a resin base material part can be suppressed. Therefore, while taking advantage of the characteristics of two types of carbon particles having different particle diameters, even a film having a resin base material portion can obtain air permeability and conductivity.

A wide variety of materials can be used for the large-diameter carbon particles 33 and the minute-diameter carbon particles 34 as long as the above-described difference in particle diameter is generated. Among them, carbon particles having a relatively uniform particle size and shape are used for stabilizing the performance. Therefore, carbon beads, spherical graphite, and carbon fibers are used as the large-diameter carbon particles 33. For the large-diameter carbon particles 33, the closer to the true density of graphite, 2.26 g / cm ³ , the better the conductivity. Therefore, the true density is preferably 2.0 g / cm ³ or more, more preferably 2.2 g / cm ³ or more. Further, carbon nanotubes and carbon black are used as the minute carbon particles 34.

  FIG. 2 is a schematic cross-sectional view of a conductive continuous porous film 1x according to another embodiment. As shown in the internal structure of the resin base material portion 10x in the illustrated example, a cavity portion 21 and a small cavity portion 23 having a smaller size (cavity diameter) than the cavity portion 21 are formed. The cavity part 21 and the small cavity part 23 originate in the to-be-removed granular material of a different particle size. For example, it can be realized by using starch particles having different particle sizes. The cavities 21, the small cavities 23, or the cavities 21 and the small cavities 23 are connected to each other to form a communication portion 22.

  Two types of carbon particles (first carbon particles 31 and second carbon particles 32) having different particle diameters are also mixed in the resin base material portion 10x of the conductive continuous porous film 1x. In the figure, the large carbon particles 33 of the first carbon particles 31 are carbon fibers, and the small carbon particles 34 of the second carbon particles 32 are carbon nanotubes. The conductive action of the conductive continuous porous film 1x is the same as that of the conductive continuous porous film 1 (see FIG. 1).

  The advantages of forming cavities of different sizes are considered as follows. When the gas permeates from one surface side to the other surface side of the conductive continuous porous film 1x (resin substrate portion 10x), the permeation of the gas in the film is complicated due to the variation in the size of the cavity. For example, the moving time or moving distance of the gas. For this reason, gas can permeate | transmit, diffusing in a film more. Therefore, in addition to the gas permeation performance due to the porosity, it can also have gas diffusion performance.

  FIG. 3 is a schematic cross-sectional view of a conductive continuous porous film 1y according to still another embodiment. As shown in the internal structure of the resin base portion 10y in the illustrated example, two types of carbon particles (first carbon particles 31 and second carbon particles 32) having different particle diameters are mixed. The first carbon particles 31 are large-diameter carbon particles 35, which are carbon beads or spherical graphite. The second carbon particles 32 are minute carbon particles 34 and are carbon nanotubes.

  A hollow portion 21 is formed inside the resin base material portion 10 y, and the hollow portions are connected to each other by a communication portion 22. The effect on the gas permeation in the conductive continuous porous film 1y is the same as that of the conductive continuous porous film 1 (see FIG. 1).

  When a granular material closer to a spherical shape is used as the large-diameter carbon particles, the flexibility and the ease of bending of the conductive continuous porous film are as shown in FIGS. Somewhat lower than film. However, it contributes to a decrease in the resistivity of the film (see Examples below). For this reason, it can be an effective film if the conditions such as use, application place and environment are taken into consideration.

  Then, the manufacturing method is mainly demonstrated about the electroconductive continuous porous film 1 disclosed in FIG. 1 using the schematic process drawing of FIG. 4 and the schematic diagram of FIG. In addition, a common name shows the same thing as the above-mentioned. The manufacturing method of the conductive continuous porous films 1x and 1y shown in FIGS. 2 and 3 is substantially the same.

  First, a predetermined amount of the granular material to be removed and the first carbon particles and the second carbon particles having different particle diameters are charged into the base resin serving as the resin base portion. The first carbon particles correspond to the large diameter carbon particles, and the second carbon particles correspond to the fine diameter carbon particles. The base resin is heated to its melting temperature and fluidized. The to-be-removed particulate matter, the first carbon particles (large-diameter carbon particles), and the second carbon particles (micro-diameter carbon particles) are sufficiently kneaded until they uniformly diffuse in the molten base resin, and the resin It becomes a kneaded product (“kneading step”). In kneading, a known blender or kneader that can be heated and melted is used. Accordingly, as the base resin, a thermoplastic resin is selected from the viewpoint of easiness of heating and melting, and in particular, a polyolefin resin and a fluororesin are selected from the viewpoint of corrosion resistance and flexibility.

  Next, the resin kneaded material is appropriately formed into a film having a film thickness, and is formed into a film-like resin molded product (“molding step”). Since the fine-diameter carbon particles are mixed in the base resin, the viscosity of the resin kneaded product tends to increase. Therefore, as a forming method for forming a film, a known forming method in the field of resin processing, such as extrusion, press forming, cold isostatic pressing (CIP), tape casting method, etc. is appropriately employed. For example, the T-die method, the tubular method, and the calendar method.

  And the to-be-removed granular material embedded in the film-like resin molding is removed, and it lose | disappears from the inside, and the void body which has a porous communication space | gap part can be obtained ("removal process"). Thereafter, the conductive continuous porous film is completed by washing, drying, cutting and the like of the voids.

  When the removed granular material is a saccharide or salt crystal, the removed granular material is dissolved and removed by watering or dipping the film-like resin molded product. The case where the to-be-removed granular material is a starch particle is further demonstrated, referring the schematic diagram of the removal process of FIG.

  Fig.5 (a) is the film-form resin molding 11 obtained by shape | molding a resin kneaded material. Since it is before a removal process, the starch particle 26 (to-be-removed granular material 25) which is a to-be-removed granular material exists in the same figure. The film-shaped resin molding 11 is immersed in a water bath containing an enzyme that degrades starch such as amylase. The water bath is heated to a temperature range suitable for enzyme reaction. For this reason, as shown in FIG. 5B, the starch particles are decomposed by the action of the enzyme and gradually shrink. Then, as shown in FIG. 5 (c), the starch as a substrate is completely decomposed and the starch particles 26 of the removed granular material disappear. As a result, the place where the starch particles 26 initially exist becomes the cavity 21. The porous communication void portion 20 is formed by communication between the hollow portions 21, and the remaining portion becomes the void body 15. Thereafter, the conductive continuous porous film is completed through washing, drying, cutting, and the like.

  In order to finally form the porous communication voids 20 by bringing the individual cavities 21 into contact with each other, for example, when the particles to be removed are starch particles, the starch particles have a weight of about 30% of the base resin weight. It is added to the extent that it accounts for 60% to 60% by weight.

  The conductive continuous porous film has a structure in which porous communication voids and carbon particles for electrical conductivity exist inside the resin base material (base resin). For this reason, the film is resistant to bending deformation due to the resin, and handling convenience and workability are remarkably improved. In addition, as disclosed in the production method, even when starch particles are employed as the particles to be removed having a relatively uniform size, the porous material can be formed under mild conditions using enzymatic decomposition. it can.

  The inventor created conductive conductive porous films of Prototype Examples 1 to 20 based on the formulation disclosed in the following table using the following raw materials. And while measuring the thickness, bending tolerance, air permeability, and resistivity of each film, overall evaluation was given also about the quality of the performance which should be provided as an electroconductive continuous porous film.

[Raw materials]
The following raw materials were used as the base resin.
Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd., Umerit 631J (melting point 121 ° C.)) (hereinafter abbreviated as LLDPE)
Polypropylene (manufactured by Nippon Polypro Co., Ltd., FW4B (melting point: 138 ° C.) (hereinafter abbreviated as PP (1))
Polypropylene (Nippon Polypro Co., Ltd., FY4 (melting point: 165 ° C.) (hereinafter abbreviated as PP (2))
Thermoplastic fluororesin (manufactured by Sumitomo 3M Limited, Dinion THV500G (melting point 165 ° C))
For each base resin, resin pellets were freeze-ground and used as powder.

The following raw materials were used as the first carbon particles.
"First carbon particles (large diameter carbon particles)"
Carbon fiber, Mitsubishi Electric Corp., DIALEAD K223SE (fiber diameter: 11 μm, true density: 2.0 g / cm ³ ) (hereinafter abbreviated as carbon fiber (1)), DIALEAD K223HE (fiber diameter) : 11 μm, true density: 2.2 g / cm ³ ) (hereinafter abbreviated as carbon fiber (2)).
Carbon beads manufactured by Nippon Carbon Co., Ltd., Nika beads ICB0520 (average particle size: 5 μm, true density: 1.35 to 1.40 g / cm ³ ), Nika beads ICB2020 (average particle size: 20 μm, true density: 1.35) To 1.40 g / cm ³ ), Nikabead ICB15020 manufactured by the same company (average particle size: 150 μm, true density: 1.35 to 1.40 g / cm ³ )
Spherical graphite Nippon Carbon Co., Ltd., Nika beads P10B-ZG (average particle size: 10 μm, true density: 2.17 g / cm ³ ), Nika beads P25B-ZG (average particle size: 25 μm, true density: 2.17 g) / Cm ³ )

The following raw materials were used as the second carbon particles.
“Second carbon particles (fine carbon particles)”
Carbon nanotubes (manufactured by Showa Denko KK, VGCF-X (fiber diameter: 10 to 15 nm), VGCF-H (fiber diameter: 150 nm) manufactured by the same company),
Carbon black (manufactured by Lion Corporation, Ketjen Black EC600JD (particle size: 34 nm))

"Other ingredients"
As the particles to be removed, potato starch (particle size: about 20-40 μm) and tapioca starch (particle size: about 10-15 μm) were used. All are manufactured by Tokai Starch Co., Ltd.
Α-amylase (Amano Enzyme Co., Ltd., Christase T5) was used as an enzyme for removing the starch particles.

  The notation of the blending ratio (wt%) in the table indicates the respective weight% (total 100 wt%) in the order of “base resin / first carbon particle / second carbon particle / particle to be removed”. The notation “0” is not included. In the preparation of each prototype, “parts by weight” is used for convenience of explanation.

[Prototype Example 1]
A powder obtained by freeze-pulverizing LLDPE was used as the base resin. A biaxial kneading extruder equipped with a T die is charged with 22 parts by weight of LLDPE, 21 parts by weight of carbon fiber (1), 10 parts by weight of carbon nanotubes, and 47 parts by weight of potato starch, and heated to 140 ° C. to form a base resin. Was melted and kneaded until each component was uniformly dispersed to obtain a resin kneaded product. The resin kneaded product was extruded from a T-die and immediately introduced between two metal rolls and formed into a film while being pressurized, and cooled to obtain a film-shaped resin molded product.

  The film-shaped resin molded product was immersed for 1 hour in a 90 ° C. hot water bath containing 1% by weight of α-amylase and adjusted to pH 6.0, and then immersed in an ultrasonic bath at 40 ° C. for 5 minutes. Washed with running water for a minute. After rinsing with water, it was dried in a dryer at 80 ° C. for 24 hours. In this way, the conductive continuous porous film (thickness 1000 μm) of Prototype Example 1 was prepared.

[Prototype Example 2]
In Prototype Example 2, the same film-like resin molded product as in Prototype Example 1 was rolled through a calender roll machine set to a linear pressure of 2 t / cm and heated to 100 ° C. to obtain a film-like resin molded product. It was. The removal of the particles to be removed was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness: 170 μm) of Prototype Example 2 was produced.

[Prototype Example 3]
In Prototype Example 3, the same film-like resin molded product as in Prototype Example 1 was used and rolled through a calender roll machine under the same conditions as in Prototype Example 2 to obtain a film-like resin molded product. The removal of the particles to be removed was the same as in Prototype Example 1. In this way, an electrically conductive porous film (thickness 80 μm) of Prototype Example 3 was produced.

[Prototype Example 4]
In Prototype Example 4, the same raw materials as in Prototype Example 1 were used, but only the blending amount was changed, and the others were made in the same manner. And the electroconductive continuous porous film (thickness 800 micrometers) of Prototype example 4 was created.

[Prototype Example 5]
In Prototype Example 5, a resin kneaded product was prepared by changing the carbon nanotubes in the resin kneaded product of Prototype Example 1 to the same amount of carbon black, and extruded from a T-die to obtain a film-like resin molded product. Thereafter, rolling by a calender roll machine and removal of particles to be removed were performed in the same manner as in Prototype Example 2. In this way, a conductive continuous porous film (thickness 80 μm) of Prototype Example 5 was prepared.

[Prototype Example 6]
In Prototype Example 6, a resin kneaded material was prepared by blending the resin kneaded material of Prototype Example 1 with carbon fiber (1) removed. Subsequent molding and removal of the particles to be removed were the same as in Prototype Example 1. Thus, a conductive continuous porous film (thickness: 400 μm) of Prototype Example 6 was produced.

[Prototype Example 7]
In Prototype Example 7, a resin kneaded material was prepared as a mixture obtained by removing potato starch as particles to be removed in the resin kneaded material of Prototype Example 1. The subsequent molding was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 300 μm) of Prototype Example 7 was prepared.

[Prototype Example 8]
In Prototype Example 8, a resin kneaded material was prepared as a mixture excluding carbon nanotubes in the resin kneaded material of Prototype Example 1. Subsequent molding and removal of the particles to be removed were the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness: 300 μm) of Prototype Example 8 was produced.

[Prototype Example 9]
In Prototype Example 9, a resin kneaded material was prepared as a composition in which the carbon nanotubes were changed to the type having a larger diameter (fiber diameter: 150 nm) in the resin kneaded product of Prototype Example 1, and an extruded film-like resin molded product was obtained from a T-die. Thereafter, rolling by a calender roll machine and removal of particles to be removed were performed in the same manner as in Prototype Example 2. Thus, an electrically conductive porous film (thickness: 200 μm) of Prototype Example 9 was produced.

[Prototype Example 10]
In Prototype Example 10, a powder obtained by freeze-pulverizing PP (1) was used as the base resin. A biaxial kneading extruder is charged with 22 parts by weight of PP (1), 19 parts by weight of carbon beads (diameter 150 μm), 12 parts by weight of carbon nanotubes, and 47 parts by weight of tapioca starch, and heated to 140 ° C. to form a base resin. Was melted and kneaded until each component was uniformly dispersed to prepare a resin kneaded product, which was extruded from a T-die to obtain a film-like resin molded product. The film-shaped resin molded product was further thinned by rolling through a calender roll machine set to a linear pressure of 2 t / cm and heated to 130 ° C. The removal of the particles to be removed was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 250 μm) of Prototype Example 10 was produced.

[Prototype Example 11]
In Prototype Example 11, a resin kneaded material was prepared by changing carbon beads having a diameter of 150 μm to carbon beads having a diameter of 20 μm in the resin kneaded material of Prototype Example 10. Thereafter, as in Prototype Example 10, it was extruded from a T die to form a film-like resin molded product, which was rolled through a calender roll machine, and the particles to be removed were removed as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 110 μm) of Prototype Example 11 was produced.

[Prototype Example 12]
In Prototype Example 12, a resin kneaded material was prepared by changing carbon beads having a diameter of 150 μm to carbon beads having a diameter of 5 μm in the resin kneaded material of Prototype Example 10. Thereafter, as in Prototype Example 10, it was extruded from a T die to form a film-like resin molded product, which was rolled through a calender roll machine, and the particles to be removed were removed as in Prototype Example 1. Thus, an electrically conductive porous film (thickness: 100 μm) of Prototype Example 12 was produced.

[Prototype Example 13]
In Prototype Example 13, in the resin kneaded product of Prototype Example 10, carbon beads having a diameter of 150 μm were changed to carbon beads having a diameter of 5 μm, and a resin kneaded product was prepared as a composition excluding carbon nanotubes. Thereafter, as in Prototype Example 10, it was extruded from a T die to form a film-like resin molded product, which was rolled through a calender roll machine, and the particles to be removed were removed as in Prototype Example 1. Thus, an electrically conductive porous film (thickness: 100 μm) of Prototype Example 13 was produced.

[Prototype Example 14]
In Prototype Example 14, a powder obtained by freeze-grinding a thermoplastic fluororesin was used as the base resin. A biaxial kneading extruder is charged with 38 parts by weight of a fluororesin, 15 parts by weight of carbon beads (diameter 5 μm), 9 parts by weight of carbon nanotubes, and 38 parts by weight of tapioca starch, and heated to 170 ° C. to melt the base resin. Then, the components were kneaded until the components were uniformly dispersed to prepare a resin kneaded product, which was extruded from a T die to obtain a film-shaped resin molded product. This film-shaped resin molded product was rolled through a calender roll machine set to a linear pressure of 2 t / cm and heated to 150 ° C. to obtain a film-shaped resin molded product. The removal of the particles to be removed was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 90 μm) of Prototype Example 14 was produced.

[Prototype Example 15]
In Prototype Example 15, powder obtained by freeze-pulverizing PP (1) as a base resin was used, and carbon fiber (1) was changed to carbon fiber (2). Carbon fiber (2) has a higher true density than carbon fiber (1) and is excellent in electrical conductivity. A biaxial kneading extruder is charged with 25 parts by weight of PP (1), 31 parts by weight of carbon fiber (2), 14 parts by weight of carbon nanotubes, and 30 parts by weight of potato starch, and heated to 170 ° C. to obtain a base resin. A resin kneaded material was prepared by melting and kneading until each component was uniformly dispersed. The resin kneaded product is extruded from a T-die and immediately introduced between two metal rollers heated to 130 ° C. under the setting of a linear pressure of 2 t / cm. Obtained. The removal of the particles to be removed was the same as in Prototype Example 1. In this way, a conductive continuous porous film (thickness 50 μm) of Prototype Example 15 was produced.

[Prototype Example 16]
In Prototype Example 16, a powder obtained by freeze-pulverizing PP (2) was used as the base resin. A biaxial kneading extruder is charged with 25 parts by weight of PP (2), 31 parts by weight of carbon fiber (2), 14 parts by weight of carbon nanotubes, and 30 parts by weight of potato starch, and heated to 180 ° C. to obtain a base resin. A resin kneaded material was prepared by melting and kneading until each component was uniformly dispersed. The resin kneaded product is extruded from a T die, immediately introduced between two metal rollers heated to 155 ° C. under a setting of a linear pressure of 2 t / cm, formed into a film shape, and cooled to obtain a film-shaped resin molded product. Obtained. The removal of the particles to be removed was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 50 μm) of Prototype Example 16 was produced.

[Prototype Example 17]
In Prototype Example 17, a resin kneaded product was prepared by changing the potato starch of the particles to be removed to tapioca starch in the resin kneaded product of Prototype Example 15. The subsequent molding was the same as in Prototype Example 15, and the removal of the particles to be removed was the same as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 50 μm) of Prototype Example 17 was produced.

[Prototype Example 18]
In Prototype Example 18, a resin kneaded product was prepared by using two types of particles to be removed in the resin kneaded product of Prototype Example 15: potato starch and tapioca starch. The weight of the starch itself was 30 parts by weight as in Prototype Example 15, and the mixing ratio was 24 parts by weight of potato starch and 6 parts by weight of tapioca starch. The raw materials and blending other than starch were the same as in Prototype Example 15, and the subsequent molding was also the same as in Prototype Example 15. The removal of starch from the particles to be removed was carried out in the same manner as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 50 μm) of Prototype Example 18 was produced.

[Prototype Example 19]
In Prototype Example 19, a resin kneaded product was prepared by changing the first carbon particles in the resin kneaded product of Prototype Example 15 from carbon fiber (1) to spherical graphite (10 μm). Other raw materials and blending were the same as in Prototype Example 15, and the subsequent molding was also the same as in Prototype Example 15. The removal of starch from the particles to be removed was carried out in the same manner as in Prototype Example 1. In this way, a conductive continuous porous film (thickness 50 μm) of Prototype Example 19 was produced.

[Prototype Example 20]
In Prototype Example 20, a resin kneaded product was prepared by changing the first carbon particles from carbon fiber (1) to spherical graphite (25 μm) in the resin kneaded product of Prototype Example 15. Other raw materials and blending were the same as in Prototype Example 15, and the subsequent molding was also the same as in Prototype Example 15. The removal of starch from the particles to be removed was carried out in the same manner as in Prototype Example 1. Thus, an electrically conductive porous film (thickness 50 μm) of Prototype Example 20 was produced.

[thickness]
Citizen Watch Co., Ltd .: MEI-10 A JIS paper thickness measuring machine was used to measure the thickness of 10 sheets of each prototype, and the thickness (μm) per sheet was calculated.

[Bending quality]
The film of each prototype was cut to 3 cm × 3 cm and bent until it became a right angle from the original flat plate shape. A prototype example in which no change occurred when bent was evaluated as “A”. A prototype example in which some cracks occurred when bent was evaluated as “B”. A prototype example that was not bendable or fractured was evaluated as “C”.

[Air permeability]
In accordance with JIS P 8117 (2009) {Paper and paperboard-Air permeability and air resistance test method (intermediate region)-Gurley method}, measurement was performed using a Gurley-type densometer type G-B2C manufactured by Toyo Seiki Co., Ltd. . Then, the time (seconds) required for air permeation was measured.

[Resistivity]
In accordance with JIS K 7194 (1994) {Resistivity testing method using conductive plastic 4-probe method}, low resistivity meter Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd., using a PSP probe The rate (Ω · cm) was measured.

[Comprehensive evaluation]
Each measurement item and evaluation were comprehensively considered, and it was evaluated whether or not the conductive communication porous film had appropriate performance. An example of a prototype with good performance was evaluated as “A”, an example of a prototype recognized as normal was “B”, and an example of an impossible prototype was evaluated as “C”. The raw materials, composition, physical properties, and evaluation of each prototype are shown in Tables 1 to 4 below.

[Discussion]
From a series of trial results, the thickness of the conductive continuous porous film can be controlled by the molding method. Therefore, 50 μm to 1000 μm could be made separately. This can meet the demand for thinning. Moreover, since the film forming and forming method of a general resin film can be diverted, the film surface can be easily smoothed.

  As in Prototyping Examples 6, 7, 8, and 13, when any one of them is missing, the performance required for the conductive continuous porous film is deteriorated or lost. Therefore, it is essential to blend two types of carbon particles having different particle sizes. In addition, it is essential because it does not become porous unless the particles to be removed are blended.

  Since the effect of the type of resin is not particularly large, a wide variety of types can be used as long as the treatment such as melting is easy. Further, from Prototype Examples 10 and 11, when the first carbon particles (large-diameter carbon particles) are particles having a large particle diameter, the air permeability decreases. From this, it is estimated that the size of the large-diameter carbon particles is suitably around 5 to 25 μm.

  From the comparison of prototype examples 15 and 17, focusing on the particles to be removed mixed in the base resin, tapioca starch has a smaller particle size than potato starch. Therefore, when starch is blended by the same weight, the inner diameter of the cavity derived from tapioca starch is narrower than that of potato starch. That is, the air flow path during ventilation is fine and complicated. The air permeability decreases accordingly. However, the diffusibility of gas or the like in the film is improved. Therefore, what kind of cavity is to be formed can be appropriately selected depending on the application location, conditions, and the like.

  Prototype Example 18 is an example in which cavities were formed using different types of particles to be removed, and the air permeability was moderate. Therefore, the permeability and diffusibility of gas passing through the film can be freely controlled.

  The film itself can be thinly formed as in Prototype Examples 15 to 20. If it does in this way, the application location of an electroconductive continuous porous film will spread further.

  The conductive continuous porous film of the present invention satisfies the requirements of good conductivity, good gas permeability, surface smoothness, corrosion resistance, and low impurities, and has new characteristics that are strong against bending and excellent in handling properties. Therefore, for example, it is promising as a material constituting a gas diffusion layer used for a polymer electrolyte fuel cell. Of course, besides this, it can be naturally used for various applications that require the characteristics of the present invention.

1, 1x, 1y Conductive communicating porous film 10, 10x, 10y Resin base material portion 15 Void body 20 Porous communication void portion 21 Cavity portion 22 Communication portion 23 Small cavity portion 25 Particles to be removed 31 First carbon particles (First carbon material)
32 Second carbon particles (second carbon material)
33,35 Large diameter carbon particles (large diameter carbon material)
34 Fine carbon particles (fine carbon material)

Claims (11)

  The resin base material portion has a porous communication gap formed by removing the particulate matter to be removed, and the resin base material portion is mixed with first carbon particles and second carbon particles having different particle diameters. A conductive continuous porous film characterized by comprising:   The conductive continuous porous film according to claim 1, wherein the resin base material portion is a thermoplastic resin.   The conductive continuous porous film according to claim 1, wherein the size of one hollow portion of the porous communication void portion is 10 μm to 50 μm.   The conductive continuous porous film according to claim 3, wherein the hollow part includes two or more kinds of hollow parts having different sizes.   The conductive continuous porous film according to claim 1, wherein the removed granular material is water-soluble particles and is removed by water content.   The conductive continuous porous film according to claim 1, wherein the particles to be removed are starch particles and are removed by enzymatic decomposition.   2. The conductive continuous porous film according to claim 1, wherein the first carbon particles are large-diameter carbon particles having a diameter of 5 μm or more, and the second carbon particles are micro-diameter carbon particles having a diameter of 10 nm or more.   The conductive continuous porous film according to claim 7, wherein the large-diameter carbon particles are carbon fibers.   The conductive continuous porous film according to claim 7, wherein the large-diameter carbon particles are spherical graphite.   The conductive continuous porous film according to claim 7, wherein the fine carbon particles are carbon nanotubes. A kneading step of kneading a base resin, a particulate to be removed, and first carbon particles and second carbon particles having different particle diameters to obtain a resin kneaded product;
A molding step of molding the resin kneaded product into a film-like resin molded product;
It has the removal process which removes the said to-be-removed granular material from the said film-form resin molding, and obtains a void body. The manufacturing method of the electroconductive continuous porous film characterized by the above-mentioned.

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